MySQL 8.0 Database Administrator — Question 47

You have semi-synchronous replication configured and working with one slave. rpl_semi_sync_master_timeout has never been reached.
You find that the disk system on the master has failed and as a result, the data on the master is completely unrecoverable.
Which two statements are true? (Choose two.)

Answer options

• A. No committed transactions are lost.
• B. The slave automatically identifies that the master is unreachable and performs any required actions so that applications can start using the slave as the new master.
• C. As soon as the incident happens, application can read data from the slave and rely on it to return a full and current set of data.
• D. Reads from the slave can return outdated data until the value of the rpi_semi_sync_master_timeout variable is reached.
• E. Reads from the slave can return outdated data for some time, until it applies all transactions from its relay log.
• F. A small amount of committed transactions may be lost in case they were committed just before the disk failure.

Correct answer: D, F

Explanation

Option D is correct because reads from the slave can be outdated until the timeout is hit, reflecting the master's last committed state. Option F is also correct as it acknowledges that transactions committed just before the failure might not be replicated to the slave, leading to potential data loss. The other options are incorrect because they either imply no data loss or suggest immediate consistency from the slave, which is not guaranteed in this scenario.